Igniting and operating circuit for discharge tubes



June 10, 1958 J. c. MOERKENS 2,838,714

IGNI TING AND OPERATING CIRCUIT FOR DISCHARGE TUBES Filed Sept. 10. 1954 v INVENTOR- JOZE F CO RNELIS MOERKENS BY v ATTORNEY Unite 2,838,714 Patented June 10, 1958 IGNITING AND OPERATING CIRCUIT FOR DISCHARGE TUBES Jozef Cornelis Moerkens, Eindhoven, Netherlands, as-

signor, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application September 10, 1954, Serial No. 455,121

Claims] priority, application Netherlands September 28, 1953 3 Claims. (Cl. 315-97) The present invention relates to an igniting and operating circuit for a pair of gas or vapor discharge tubes.

, One circuit of the foregoing type comprises two gaseous or vapor discharge tubes stabilized capacitively and inductively, respectively, the tubes including thermionic electrodes connected to secondary windings of a transformer, of which the primary winding is connected in series with the series-impedance of the tube stabilized inductively. This arrangement affords the advantages of a satisfactory power factor, a small stroboscopic effect and a common heating-current transformer which cannot be overloaded by a direct-current component of the tube stabilized capacitively. The seriesimpedance of the tube stabilizedinductively and the primary winding of the heating-current transformer, which are connected in series, constitute an inductive voltage-divider. Consequently, when potential is applied to the circuit, the voltage set up across the primary winding is smaller than the supply voltage, so that the tube stabilized inductively, which is connected in parallel therewith, is ignited less readily than at the full supply voltage. As a matter of fact, the voltage set up at the inductively-stabilized tube may be increased by transformation, but in this case the discharge current of the tube traverses the heating-current windings and this implies an undesirable overload thereof.

The chief object of the invention is to provide a circuit obviating the above-mentioned difiiculties. of the present invention exhibits the characteristic that the circuit of the tube stabilized capacitively is connected, in series with part of the series-impedance of the tube stabilized inductively, to the terminals of the source of potential, and that the heating-current windings of the tube stabilized capacitively are connected in such manner that, when potential is applied to the circuit, the voltage set up at the tube stabilized capacitively is higher than the voltage of the source, whereas the heating-current windings of the tube stabilized inductively are connected in such manner that, when the potential is applied, the voltage set up at the tube stabilized inductively is not higher than the voltage across the primary winding of the heating-current transformer.

This arrangement results in an increased voltage for the ignition of the tube stabilized capacitively, so that this tube is ignited first. After the ignition thereof, its discharge current traverses part of the series-impedance of the tube stabilized inductively and this part constitutes the primary winding of a transformer which supplies an increased voltage for the ignition of the tube stabilized inductively.

Further, the discharge current of a discharge tube flows via those extremities of the thermionic electrodes which exhibit, relatively, the highest potential difference. Now, due to the fact that the primary winding of the common heating-current transformer is connected in parallel with the tube stabilized inductively, the voltages of all the heating-current windings during normal operation are in phase with the operating voltage of said tube. Conse- The circuit qucntly, the heating-current windings of the tube stabilized capacitively no longer bring about an increase in the voltage on this tube during normal operation, so that neither the heating-current windings of the capacitivelystabilized tube nor those of the tube stabilized inductively are traversed by the discharge current.

In order to ensure that the tube stabilized capacitively is ignited first, the number of heating-current turns of this tube may be larger than that of the tube stabilized inductively.

In order that the invention may be readily carried into etfect it will now be described with reference to the accompanying drawing, wherein:

Fig. l is a schematic circuit diagram of an embodiment of the arrangement of the present invention; and

Fig, 2 is a voltage diagram of the circuit of Fig. l during normal operation.

In Fig. 1, reference numerals 1 and 2 indicate two gaseous or vapor-discharge tubes, for example, 40 watt fluorescent lamps; that is to say, low-pressure mercuryvapor discharge tubes of about 120 ems. in length and about 4 cms. in diameter, which tubes also contain a rare gas, for example, argon, at a few millimeters pressure and of which the walls are coated with materials by which the radiation produced in the discharge are converted into radiation of longer wavelength. During normal operation, the operating voltage of such tubes is about volts and the discharge current is about 0.43 ampere.

Tube 1 is connected to terminals 3 and 4 of a suitable source of potential via the series-combination of an inductance 5, a capacitor 6 and a part of an inductance 7. The capacitative reactance of the capacitor 6 is higher than the total inductive reactance of the inductance coil 5 and that portion of the inductance coil 7 which is located between the points 3 and 71, so that the tube 1 is stabilized capacitively; that is to say, its discharge current leads with respect to a supply voltage or" 220 volts,

50 cycles, of which 3.and 4 represent the terminals. It is to be noted that the mutual sequence of the elements 5 and 6 is immaterial. Tube 2 is stabilized inductively by means of the inductance 7.

Each of the tubes 1 and 2 comprise thermionic electrodes 11, 12 and 21, 22, respectively, which are connected to secondary windings 13, 14 and 23, 24, respectively, of a transformer 8, of which the primary winding 9 is connected via inductance 7 to the terminals 3 and 4. The primary winding 9 is connected directly in parallel with the tube 2. The ends of the primary winding 9 also constitute the heating-current windings 23 and 24. However, if desired, the windings 23 and 24 could alternatively be formed as separate windings which are so connected to the primary winding that the maximum voltage set up across tube 2 is not higher than the voltage across the primary winding 9.

The heating-current windings 13 and 14 are formed as separate windings and are connected to the capacitor 6 and the terminal 4, respectively, in such manner that the voltage set up at the tube 1, which has not yet ignited, is higher than the applied voltage between the terminals 3 and 4.

In one specific embodiment, for example, the circuit was proportioned as follows for a supply voltage of 220 volts, 50 cycles per second, and the use of two 40 watt fluorescent lamps. The inductance 5 had an impedance of about 250 ohms at 0.44 ampere, the capacitor 6 had an impedance of about 630 ohms at 0.44 ampere, and the inductance 7 had an impedance of about 420 ohms at 0.44 ampere with a total number of 1530 turns, of which 300 were located between the points 3 and 71. The heating-current transformer 8 comprised 1720 primary turns, of which 60 turns at each extremity served as the heating-current windings 23 and 24, respectively. The transformer also included two separate windings 13 and 14, each of 100 turns.

When voltage is applied to the circuit, the voltage set up at tube 1 is about 232 volts and that at tube 2 is about 196 volts. The device then absorbs only the primary current of about 0.1 ampere of the heating-current transformer, the heating current of the electrodes 11, 12 being about 0.43 ampere, and that of the electrodes 21, 22 being about 0.35 ampere. Under these conditions, the tube 1 is ignited first. Its discharge current flows via the part of inductance 7 located between the points 3 and '71 thus causing the voltage across winding 9 and tube 2 to be increased up to about 236 volts and the heating current traversing the electrodes 21 and 22 to be increased up to about 0.42 ampere. This leads to ignition of tube 2. In the normal operating condition that now prevails, only the operating voltage of about 110 volts of tube 2 is set up across primary winding 9, so that the heating currents of the electrodes also decrease proportionally.

Fig. 2 shows the voltage diagram of this device during normal operation. For the sake of simplicity, it is assumed that point 71 coincides with point 3. The supply voltage E lags by about 60 with respect to the operating voltage E of the'tube 1 stabilized capacitively, and leads by about 60 with respect to the operating voltage E of the tube 2 stabilized inductively. E and E -indicate the voltages across the elements 5, 6 and across the inductance 7, respectively. The voltages E E E E of the corresponding heatingcurrent windings are directed in the same sense as the operating voltage E of the tube stabilized inductively.

'The discharge applies to those extremities of the electrodes between which the highest potential difference prevails. As may be seen from Fig. 2, these are in both tubes 1 and 2 those extremities which are connected directly to a series-impedance and the supply voltage,'re spectively. Consequently, there is no flow of discharge current through a heating-current winding. Furthermore, due to the fact that the heating-current windings of the tube stabilized capacitively are provided on a transformer, the primary winding of which is connected in parallel with the tube stabilized inductively, the heating-current windings may be connected in such manner that they supply an increased ignition voltage and nevertheless are not traversed by the discharge current.

In order to facilitate ignition, the tubes 1 and 2 may have provided on their walls ignition electrodes (not 4 shown) which are electrically connected, if desired, to ground or to a thermionic electrode.

While I have described my invention in connection with specific embodiments and applications, other modifications thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. An igniting and operating circuit arrangement for two discharge tubes each having an ionizable medium and a pair of thermionic electrodes, said circuit arrangement comprising input means for a source of potential, an inductive impedance connected in series with a first of said tubes to said input means, a capacitative impedance connected in series with the second of said tubes and a portion or" said inductive impedance to said input means, said portion of said inductive impedance comprising less than the whole of the said inductive impedance, a transformer having a primary winding and having a plurality of secondary windings each connected to and energizing a respective one of said thermionic electrodes, said primary winding being connected in shunt with said first tube and in series with said inductive impedance to said input means, the secondary windings energizing the thermionic electrodes of said first tube being poled to produce across said first tube a voltage having a value not higher than the voltage across said primary winding, and the secondary windings energizing the thermionic electrodes of said second tube being poled to produce across said second tube a voltage having a value greater than the potential of said source.

2. A circuit arrangement as claimed in claim 1, wherein said secondary windings energizing the thermionic electrodes of said second tube'have a greater number of turns than the secondary windings energizing the thermionic electrodes of said first tube.

3. A circuit arrangement as claimed in claim 1, wherein said primary winding and the secondary windings energizing the thermionic electrodes of said first tube are windings of an autotransformer.

References Cited in the file of this patent UNITED STATES PATENTS 2,025,471 Osborne Dec. 24, 1935 2,504,549 Lemmers Apr. 18, 1950 2,505,288 Hall Apr. 25, 1950 2,683,240 Strange July 6, 1954 

